TAPPING AND SPLICING WIRES:

Here is my quick guide to tapping into and splicing wiring in your automobile.  Mechanical joints are best suited for vibration and resistance to the elements.  While soldering is not recommended, since it fatigues easily, you can still get away with it as long as you don’t allow the solder to wick up into the insulation.  You will then need to insulate your soldered joints to ward off corrosion.  I personally like to use dielectric grease and heat shrink tubing when I have the time...

First of all, I'd like to state that these are CRAP: Vampire taps tend to damage the wire beneath the insulation or generally give a bad connection, ESPECIALLY under the hood of a car in the elements.  I suggest throwing these taps as far as you can. (Or at least into the nearest trash bin...) If you plan on modifying your car's wiring with any regularity, I suggest purchasing some good quality strippers and crimpers. These are cheap and sometimes of poor quality, but they might do... Sometimes...

Personally, I use Klein and Crimpmaster for the best connections using generic crimps. Specialized and military-type crimps sometimes require a specialized crimp tool that can cost in excess of $300!

Here are some generic wire joining crimps.  They are a fair choice for quickly joining two or more wires and are considered semi-permanent.  I fill them with dielectric or silicone grease before inserting wire to ensure a more corrosion resistant joint. The color of the insulation on the crimps isn't actually for looks... It describes what size wire is appropriate for the connector: Red = 22-18 AWG Blue = 16-14 AWG Yellow = 12 -10 AWG The colors do repeat as you get into bigger wire, but most of these connectors are not commonly found under the hood... Butt splice connectors filled with silicone grease are good for under hood wiring:

HERE’S HOW I GET IT DONE:

Start by selecting the next size bigger wire on your strippers and make a cut, being careful not to actually cut the wire. Make another cut approximately 1” away from the first cut. Using a knife blade, make a longitudinal incision through the insulation, connecting the two previous cuts. Remove the insulation, and inspect the wire for damage. Separate the strands into equal parts and spread them apart to form an eyelet. Insert your third wire through the eyelet and close it up. Wrap the third wire around the eyelet... ...and pull it tight. Just before taping up the connection with quality 3M Scotch Super 88 tape, you can solder the joint, but be very careful not to wick the solder up into the insulation.  This will fail over time from vibration.